Solid oxide fuel cell with internal reformer

Abstract

An individual solid oxide cell (SOC) constructed of a sandwich configuration including in the following order: an oxygen electrode, a solid oxide electrolyte, a fuel electrode, a fuel manifold, and at least one layer of mesh. In one embodiment, the mesh supports a reforming catalyst resulting in a solid oxide fuel cell (SOFC) having a reformer embedded therein. The reformer-modified SOFC functions internally to steam reform or partially oxidize a gaseous hydrocarbon, e.g. methane, to a gaseous reformate of hydrogen and carbon monoxide, which is converted in the SOC to water, carbon dioxide, or a mixture thereof, and an electrical current. In another embodiment, an electrical insulator is disposed between the fuel manifold and the mesh resulting in a solid oxide electrolysis cell (SOEC), which functions to electrolyze water and / or carbon dioxide.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. provisional patent application No. 62 / 411,792, filed Oct. 24, 2016, which is incorporated in its entirety herein by reference.GOVERNMENT RIGHTS[0002]This invention was made with U.S. government support under Contract No. NNX15CC43P, awarded by the National Aeronautics and Space Administration. The U.S. Government has certain rights in the invention.FIELD OF THE INVENTION[0003]In one aspect, this invention pertains to a solid oxide cell (“SOC”), more particularly, to a solid oxide fuel cell (“SOFC”) and to its reverse embodiment, a solid oxide electrolysis cell (“SOEC”). Even more particularly, this invention pertains to a solid oxide fuel cell having integrated therein a fuel reformer and to its reverse embodiment, a solid oxide electrolysis cell having integrated therein a heater. In another aspect, this invention pertains to a method of generating electricity in the solid oxide fuel cell having...

AI Technical Summary

Benefits of technology

The solid oxide fuel cell of this patent avoids the need for an external reformer and associated balance of plant components, reducing weight and complexity. The reformer is a separate catalytic layer of mesh on or adjacent to the fuel manifold, providing simplified manufacture and uniform temperature throughout the cell repeat unit and stack assembly. The mesh structure provides rapid heat input for start-up and effective heat removal during steady state operation. The embedded reformer produces hydrogen and carbon monoxide, resulting in increased power density, higher fuel utilization, and long-term performance. The design is adaptable to various manufacturers' solid oxide stacks and allows for fuel exhaust recycle and water neutral operation. The electrolysis cell and process provide rapid heat input and temperature uniformity for the endothermic electrolysis process.

Problems solved by technology

Since gaseous hydrogen and carbon monoxide require pressurization and are not readily available as transport fuels, these gaseous fuels impose limitations on the size and portability of the fuel cell.

Particulate catalysts are disadvantageously cumbersome, weighty and prone to attrition losses.

The coated and dispersed designs placed directly on the interconnect and fuel electrode are difficult to manufacture.

Additionally, both prior art designs have problems in that reforming capability often interferes with the expected capability of the fuel cell part; for example, the oxidation reaction at the fuel electrode or current collection at the interconnect is diminished.

Moreover, coating the fuel electrode or interconnect with a reforming catalyst often diminishes reforming capability, which leads to poisoning of the reforming and fuel cell parts via coking.

It should be further appreciated that start-up of prior art solid oxide fuel cells undesirably involves a significant amount of time.

Prior art solid oxide fuel cells lack rapid and efficient heat input and heat withdrawal mechanisms.

This mode also has the advantage to operate at higher current density resulting in reduced system size; but may, however, lead to premature ageing of system components.

Generally, the disposition of the heaters in prior art apparatuses does not provide for uniform heating of each cell repeat unit in the stack.

This can result in hot or cold spots in the stack that stress one part of the stack more than another and ultimately either degrade the stack or crack a single or multiple solid oxide cells within the stack.

Even more importantly, the reformer should operate with a conversion efficiency greater than about 80 percent in a single pass in converting the hydrocarbon fuel to hydrogen and carbon monoxide, else the resulting reformate contains a disadvantageously high concentration of unconverted hydrocarbon, which at SOFC operating temperatures potentially cokes and critically damages the fuel electrode.

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